1. Field of the Invention
The present invention relates to the operation of power converters for supplying electrical power to a grid and, in particular, to a frequency converter of a generator of a wind energy turbine.
2. Related Prior Art
Electrical power in public power grids is supplied by diverse energy sources converting mechanical energy into electrical energy. The main energy sources supporting public power grids are coal power plants and nuclear power plants. Several other types of energy sources, in particular power plants of regenerative energy like solar power plants, water power plants or wind energy turbines, also contribute to support the public power grid.
In the past, in the event of a significant grid voltage drop in a public power grid, it was required that in such an event wind energy turbines are shut down automatically. However, due to the increased number of wind energy turbines it becomes more and more important that these turbines support the public power grid in the event of a substantial grid voltage drop. However, due to thermal stresses applied to the electronic components of the frequency converter of a generator converting mechanical energy into electrical energy, increasing the output current of the converter in the event of a grid voltage drop is critical and limited.
Accordingly, it is an object of the present invention to increase the output current of a generator in particular of a wind energy turbine in the event of a substantial grid voltage drop.